Task async await

暇之余，究多Task、async、await。

using System;

using System.Collections.Generic;

using System.Linq;

using System.Linq.Expressions;

using System.Text;

using System.Threading;

using System.Threading.Tasks;

namespace ConsoleApp2

{

    class Program

    {

        static void Main(string[] args)

        {

            for (int i = ; i < ; i++)

            {

                Task.Run(() => Run2()); //类似于线程池，开启线程小于5

            }

            for (int i = ; i < ; i++)

            {

                new Thread(Run1).Start();//开启5个线程

            }

            Task<string> task = Task.Run(

                () => Thread.CurrentThread.ManagedThreadId + ""

            );

            Console.WriteLine(task.Result);//task.Result 会等到task执行完毕执行

            Console.WriteLine("-------主线程启动-------");

            Task<int> task2 = GetStrLengthAsync();

            Console.WriteLine("主线程继续执行");

            Console.WriteLine("Task返回的值" + task2.Result);

            Console.WriteLine("-------主线程结束-------");

        }

        static void Run1()

        {

            Console.WriteLine("Thread Id =" + Thread.CurrentThread.ManagedThreadId);

        }

        static void Run2()

        {

            Console.WriteLine("Task调用的Thread Id =" + Thread.CurrentThread.ManagedThreadId);

        }

        //async必须返回void Task Task<int>

        static async Task<int> GetStrLengthAsync()

        {

            Console.WriteLine("GetStrLengthAsync方法开始执行");

            //await 必须用来修饰Task Task<TResult>,而且只能出现在async修饰的异步方法中。

            //遇到await并未开启新线程，而是遇到GetString方法中的Task.Run()时才开启了新线程

            string str = await GetString();

            Console.WriteLine("GetStrLengthAsync方法结束执行");

            return str.Length;

        }

        static Task<string> GetString()

        {

            Console.WriteLine("GetString方法开始执行");

            return Task.Run(() =>

            {

                Thread.Sleep();

                return "GetString返回值";

            });

        }

    }

}